We attempt to determine the role of human and rabbit keratocytes in the synthesis of components of corneal stromal matrix. Methods to obtain stromal cells in high yield have been developed from human and rabbit corneas, thus avoiding problems of "in vitro" senescence. We are concentrating on the simultaneous study of the synthesis and characterization of collagen and proteoglycans by these cells in culture. Investigation of different metabolic states of the keratocytes seem to parallel observations in developing or regenerating corneal stroma. Methods used in our studies include, among others, standard histological techniques, cryogenic storage, use of radioactive precursor of collagen and proteoglycans, cell fractionation, preparative and analytical ultracentrifugation techniques, specific enzymatic digestions, column and paper chromatography and gel electrophoresis. This project may contribute to the understanding of functions of the keratocytes and the possible role of the regulation of the synthesis of macromolecules in the maintenance of corneal transparency.